Cylinder injection type internal combustion engine, control method for internal combustion engine, and fuel injection valve

ABSTRACT

There is provided a cylinder injection type internal combustion engine capable of performing stratified charge operation at the time of a vehicle speed of 120 km/h and/or an engine rotational speed of 3200 rpm to enhance the fuel efficiency and/or to observe the emission regulations. In the internal combustion engine, a stratum of air and/or air flow is formed between a fuel spray injected from an injection valve and the top face of a piston and/or the wall surface of a combustion chamber, and a face shape contrived to guide the air flow is formed on the top face of the piston.  
     Also, the stratified charge operation can be performed even at the time of cold start or cranking.

TECHNICAL FIELD

[0001] The present invention relates to a cylinder injection typeinternal combustion engine in which fuel is injected directly into acombustion chamber of an internal combustion engine, a control methodfor an internal combustion engine, and a fuel injection valve.

BACKGROUND ART

[0002] In a conventional internal combustion engine of this type, aprojecting portion is formed in the center on top face of a piston toform a depression called a cavity in the piston. Thereupon, fuel isinjected from a fuel injection valve toward this cavity in the piston atthe second half stage of the compression stroke of the internalcombustion engine, so that a fuel spray repelled by the cavity isconcentrated in the direction of ignition plug (Society of AutomotiveEngineers of Japan Annual Proceedings 976, Paper No. 9740307, October,1997).

[0003] Thus, the stratification of fuel in the combustion chamber isachieved, and combustion can be produced even with a lean mixture of anair-fuel ratio of about 40. Usually, such a combustion process isreferred to as a stratified charge lean burn operation, which serves forreducing fuel consumption at the time of low-load operation of theinternal combustion engine.

[0004] Also, JP-A-7-119507 has disclosed a combustion system in which atthe time of high-load operation, the operation is switched to aso-called homogeneous operation in which fuel is injected during theintake stroke so that the fuel is distributed uniformly in the whole ofthe combustion chamber.

[0005] Further, JP-A-6-81656, JP-A-10-110660, JP-A-7-293259,JP-A-10-30441, JP-A-10-169447, and JP-A-10-896, and U.S. Pat. No.5,850,816 have disclosed a combustion system in which a tumble air flowis produced in the combustion chamber, and a fuel spray is concentratedaround the ignition plug by this tumble air flow.

[0006] However, even if any of the above-described combustion systems isused, most of fuel injected from the injection valve sticks to thepiston and the wall surface in the combustion chamber, so that there arelimitations in increasing fuel efficiency and reducing harmfulcomponents (for example, hydrocarbon) in exhaust gas due to thestratified charge operation.

[0007] Also, the stratified charge operation cannot be provided under acondition of 80 km/h or 2400 rpm and higher.

[0008] A first object of the present invention is to reduce fuelsticking to the piston and the wall surface in the combustion chamberand to decrease HC in exhaust gas.

[0009] A second object of the present invention is to increase theoutput at the time of homogeneous operation.

[0010] A third object of the present invention is to provide a fuelinjection valve for cylinder injection, in which less fuel sticks to thepiston.

[0011] A fourth object of the present invention is to enable thestratified charge operation even at a vehicle speed of 80 km/h andhigher or at an engine rotational speed of 2400 rpm and higher (forexample, in a high speed region where the vehicle speed is 120 km/h orthe engine rotational speed is 3200 rpm).

DISCLOSURE OF THE INVENTION

[0012] The above first object is attained by a cylinder injection typeinternal combustion engine comprising a combustion chamber into whichair is sucked; a fuel injection valve for injecting fuel directly intothe combustion chamber; and a piston for changing the volume of thecombustion chamber, whose central portion of top face is equal in heightto or lower than the surroundings, characterized in that a stratum ofthe sucked air or a stratum of air flow is interposed between a fuelspray injected from the fuel injection valve and the piston.

[0013] Also, the above first object is attained by a cylinder injectiontype internal combustion engine comprising a fuel injection valve forinjecting fuel directly into a combustion chamber of the internalcombustion engine, characterized in that penetration of a fuel sprayinjected from the fuel injection valve into the combustion chamber isset to be shorter than a distance between the top face of a pistonreciprocating in the combustion chamber and a fuel discharge port of thefuel injection valve during a period of time from the start of injectionto the completion of injection of fuel.

[0014] Also, the above first object is attained by a cylinder injectiontype internal combustion engine comprising a fuel injection valve forinjecting fuel directly into a combustion chamber of the internalcombustion engine, the fuel injection valve being formed so that thepenetration of a fuel spray 3.8 msec after the injection of fuel to theatmosphere of the atmospheric pressure is 60 mm or shorter.

[0015] Also, the above first object is attained by a cylinder injectiontype internal combustion engine comprising a fuel injection valve forinjecting fuel directly into a combustion chamber of the internalcombustion engine, the fuel injection valve being formed so that a fuelspray with a Zauter mean particle size of 20 μm or smaller is injected.

[0016] Also, the above first object is attained by a cylinder injectiontype internal combustion engine, comprising a combustion chamber for theinternal combustion engine into which air is sucked through an intakevalve; a fuel injection valve for injecting fuel directly into thecombustion chamber; swirl flow generating means for generating an airflow in the combustion chamber; and operation condition detecting meansfor detecting the operation condition of the internal combustion engine,the internal combustion engine having a control unit for supplying afuel injection valve driving signal to the fuel injection valve so thatfuel is injected at the second half stage of the compression stroke whenthe detected operation condition is at a low load.

[0017] Also, the above second object is attained by a cylinder injectiontype internal combustion engine comprising a combustion chamber of theinternal combustion engine, into which air is sucked through an intakevalve; a fuel injection valve for injecting fuel directly into thecombustion chamber; swirl flow generating means for generating a swirlair flow in the combustion chamber; and operation condition detectingmeans for detecting the operation condition of the internal combustionengine, the internal combustion engine having a control unit forsupplying a fuel injection valve driving signal to the fuel injectionvalve so that fuel is injected on the intake stroke when the detectedoperation condition is at a medium load.

[0018] Also, the above second object is attained by a cylinder injectiontype internal combustion engine comprising a combustion chamber of theinternal combustion engine, into which air is sucked through an intakevalve; a fuel injection valve for injecting fuel directly into thecombustion chamber; and operation condition detecting means fordetecting the operation condition of the internal combustion engine, theinternal combustion engine having a control unit for supplying a fuelinjection valve driving signal to the fuel injection valve so that fuelis injected for a period of time when the intake air velocity is lowerthan the spray velocity on the intake stroke when the detected operationcondition is at a high load.

[0019] Also, the above second object is attained by a cylinder injectiontype internal combustion engine comprising an upstream swirl type fuelinjection valve for injecting fuel directly into a combustion chamber ofthe internal combustion engine; and operation condition detecting meansfor detecting the operation condition of the internal combustion engine,the internal combustion engine having a control unit for supplying afuel injection valve driving signal to the fuel injection valve so thatfuel is injected at a time for a period of time when the intake airvelocity is higher than the spray velocity on the intake stroke when thedetected operation condition is at a high load.

[0020] Also, the above first object is attained by a control method fora cylinder injection type internal combustion engine, in which when theoperation condition of the internal combustion engine is at a low load,a swirl air flow is generated in a combustion chamber, fuel is injectedat the first half stage of the compression stroke, and a rich mixturestratum is formed inside the swirl air flow, whereby stratified chargelean operation is performed.

[0021] Also, the above second object is attained by a control method fora cylinder injection type internal combustion engine, in which when theoperation condition of the internal combustion engine is at a mediumload, a swirl air flow is generated in a combustion chamber, fuel isinjected on the intake stroke, and a mixture with a homogeneousconcentration is generated in the combustion chamber by the swirl airflow, whereby homogeneous lean operation is performed.

[0022] Also, the above second object is attained by a control method fora cylinder injection type internal combustion engine, in which when theoperation condition of the internal combustion engine is at a high load,fuel having an amount capable of achieving a stoichiometric air-fuelratio is injected for a period of time when the intake air velocity islower than the spray velocity on the intake stroke, and a mixture with ahomogeneous concentration is generated in the combustion chamber byintake air, whereby homogeneous stoichiometric operation is performed.

[0023] Also, the above third object is attained by a fuel injectionvalve for injecting fuel directly into a combustion chamber of aninternal combustion engine, characterized in that a fuel spray injectedfrom the fuel injection valve has a penetration of 60 mm or shorter 3.8msec after the time when fuel is injected to the atmosphere of theatmospheric pressure.

[0024] Also, the above third object is attained by a fuel injectionvalve for injecting fuel directly into a combustion chamber of aninternal combustion engine, characterized in that the spray particlesize of fuel injected from the fuel injection valve is 20 μm or smallerin terms of Zauter mean particle size.

[0025] Further, the above fourth object is attained by a cylinderinjection type internal combustion engine comprising a combustionchamber into which air is sucked; a fuel injection valve for injectingfuel directly into the combustion chamber; and a piston for changing thevolume of the combustion chamber, characterized in that an air flow isgenerated in the combustion chamber to form a stratum of the sucked airor a stratum of air flow between a fuel spray injected from the fuelinjection valve and the piston, and a guide face for guiding the flow onthe top face of piston to a position just under the injection valve.

[0026] Specifically, the object is attained by a cylinder injection typeinternal combustion engine comprising air flow generating means forgenerating a tumble air flow in a combustion chamber of the engine; apiston having a top face shape contrived so as to guide the air flowgenerated in the combustion chamber from the side distant from a fuelinjection valve to a position just under the fuel injection valve alongthe top face of the piston; and the fuel injection valve for supplying afuel spray to the outer stratum of the air flow extending from the fuelinjection valve to an ignition plug.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is a schematic view showing an engine system;

[0028]FIG. 2 is a block diagram (1);

[0029]FIG. 3 is a block diagram (2);

[0030]FIG. 4 is a view showing an operation region map;

[0031]FIG. 5 is a view showing a swirl flow in a combustion chamber;

[0032]FIG. 6 is a view showing an installation position of a subsidiaryintake air passage;

[0033]FIG. 7 is a view showing a relationship between the subsidiaryintake air passage and the swirl flow;

[0034]FIG. 8 is a view showing a relationship between the injectiondirection and the swirl flow;

[0035]FIG. 9 is a view showing another method for producing a swirlflow;

[0036]FIG. 10 is a diagram showing a control method at the time of leanburn operation;

[0037]FIG. 11 is a diagram showing fuel spray characteristics;

[0038]FIG. 12 is a view showing the outline of the observation result ofspray behavior;

[0039]FIG. 13 is a diagram showing a relationship between intake airvelocity and injection pulse at the time of full-open operation;

[0040]FIG. 14 is a view showing a comparison between single injectionand divided injection;

[0041]FIG. 15 is a diagram showing a relationship between the intensityof swirl flow and the injection pulse;

[0042]FIG. 16 is a diagram showing a relationship between intake airvelocity and injection pulse at the time of full-open operation;

[0043]FIG. 17 is a block diagram of a four-hole diffusion type nozzle;

[0044]FIG. 18 is a block diagram of a hole position shifting typenozzle;

[0045]FIG. 19 is a block diagram of a multi-hole type nozzle;

[0046]FIG. 20 is a block diagram of a flow path change type nozzle;

[0047]FIG. 21 is a block diagram of a fuel swirl type nozzle havingsquare holes;

[0048]FIG. 22 is a block diagram of a fuel swirl type nozzle havinground holes;

[0049]FIG. 23 is a block diagram of a slit type nozzle;

[0050]FIG. 24 is a block diagram of a four-hole slit type nozzle;

[0051]FIG. 25 is a block diagram of another four-hole slit type nozzle;

[0052]FIG. 26 is a block diagram of a two-hole slit type nozzle;

[0053]FIG. 27 is a block diagram of a four-hole independent swirl typenozzle;

[0054]FIG. 28 is a block diagram of a four-hole collision type nozzle;

[0055]FIG. 29 is a block diagram of an eight-hole collision type nozzle;

[0056]FIG. 30 is a block diagram of a spray resonance type nozzle;

[0057]FIG. 31 is a block diagram of another spray resonance type nozzle;

[0058]FIG. 32 is a block diagram of a flow path change type nozzle;

[0059]FIG. 33 is a perspective view showing an engine configuration inaccordance with the embodiment;

[0060]FIG. 34 is a view showing one example (long subsidiary intake airpassage) of air flow generating means, FIG. 34(a) being a top view, andFIG. 34(b) being a side view;

[0061]FIG. 35 is a view showing one example (short subsidiary intake airpassage) of air flow generating means, FIG. 35(a) being a top view, andFIG. 35(b) being a side view;

[0062]FIG. 36 is a view showing one example (notched valve) of air flowgenerating means, FIG. 36(a) being a top view, and FIG. 36(b) being aside view;

[0063]FIG. 37 is a view showing one example (notched valve+gate valve)of air flow generating means, FIG. 37(a) being a top view, and FIG.37(b) being a side view;

[0064]FIG. 38 is a graph showing a comparison of tumble ratios of airflow generating means;

[0065]FIG. 39 is a perspective view showing an air flow in a combustionchamber in the case of flat piston;

[0066]FIG. 40 is a perspective view showing a shape of an improvedpiston;

[0067]FIG. 41 is a schematic view showing a transfer behavior of fuelspray in accordance with the embodiment;

[0068]FIG. 42 is a side view showing a relationship between engine shapeand fuel spray;

[0069]FIG. 43 is a graph showing a relationship between top end angleunder a pressurized condition and engine performance;

[0070]FIG. 44 is an explanatory view for definition of injection angle;

[0071]FIG. 45 is a view showing a configuration of an impulse swirlmeter;

[0072]FIG. 46 is a perspective view showing one example of a directinjection type engine using the present invention; and

[0073]FIG. 47 is a schematic view in which FIG. 46 is viewed from abovethe combustion chamber.

BEST MODE FOR CARRYING OUT THE INVENTION

[0074] Embodiments of the present invention will be described withreference to the accompanying drawings.

[0075]FIG. 1 shows one example of an engine system to which the presentinvention is applied. An engine 11 has a crank mechanism comprising of aconnecting rod 14 and a crankshaft 15, and a combustion chamber 13 isformed by a piston 12 connected to the crank mechanism and an enginehead of the engine 11. The combustion chamber 13 is sealed by intakevalves 27, exhaust valves 29, an ignition plug 28, and a fuel injectionvalve 26 which are installed on the engine head.

[0076] In the engine 11, air necessary for combustion is sucked into thecombustion chamber 13 by the reciprocating motion of the piston 12. Dirtand dust contained in the air to be sucked are removed by an air cleaner18, and an intake air amount, which is a basis for calculating a fuelinjection amount, is measured by an air flow sensor 19. The intake airamount is controlled by the degree of opening of a throttle valve 20,and the air to be sucked passes through a main intake air passage 21 anda subsidiary intake air passage 22 according to the operation conditionof the engine 11. A control unit 36 for controlling the engine 11 issupplied with a crank angle signal sent from crank angle sensors 16 and17 and an acceleration stroke sent from an accelerator position sensor38. Besides, as shown in FIG. 2, the control unit 36 is supplied withvarious pieces of information such as an intake air amount signal sentfrom the air flow sensor 19, an A/F signal sent from an air-fuel ratiosensor 31 installed in an exhaust pipe, and an exhaust catalysttemperature signal sent from a temperature sensor 32.

[0077] The control unit 36 detects the operation condition of the engine11 based on the information such as the crank angle signal andacceleration stroke, and determines the fuel injection amount, injectiontiming, and ignition timing based on the operation condition. Anignition coil 34 generates a high voltage according to an ignitionsignal sent from the control unit 36, and produces an ignition spark bymeans of the ignition plug 28. A fuel injection valve drive unit 35amplifies an injection signal sent from the control unit 36 to drive thefuel injection valve 26. Fuel is supplied from a high-pressure fuel pump24, which is driven by the engine 11, to the fuel injection valve 26through a fuel pipe 25.

[0078] In order to form a necessary swirl flow in the combustion chamber13 according to the operation condition of the engine 11, the degree ofopening of a flow dividing valve 23 in the main intake air passage 21 iscontrolled to regulate the amount of air introduced from the subsidiaryintake air passage 22. To open and close the flow dividing valve, a flowdividing valve driving signal VD is sent from the control unit 36according to the operation condition of the engine. The air passingthrough the subsidiary intake air passage 22 has a high speed anddirectivity, so that it forms a necessary swirl flow in the combustionchamber 13. By opening the flow dividing valve 23, air flows through themain intake air passage 21, and the air passing through the subsidiaryintake air passage 22 lessens. Thereby, the intensity of the swirl flowformed in the combustion chamber 13 is regulated.

[0079]FIGS. 2 and 3 are block diagrams showing the flow of controlsignals. The flow of control signals in the engine control unit 36 willbe described with reference to these figures.

[0080] In block 361, the crank angle signal, the acceleration strokeθ_(α), etc. are taken and held, an engine rotational speed Ne iscalculated from the crank angle signal, and a target torque T of theengine is calculated from the acceleration stroke θ_(α) and the enginerotational speed Ne. In blocks 362, 363 and 364, a fuel injection pulsewidth Tp, fuel injection start timing IT, and ignition timing θ_(Ad) aredetermined from the engine rotational speed and the target torque heldin the block 361. The fuel injection amount is substantiallyproportional to the fuel injection pulse width Tp. The fuel injectionpulse width Tp and the fuel injection start timing IT are, as shown inFIG. 4, determined from a map of the engine rotational speed Ne and thetarget torque T. Signals (fuel injection valve drive signals) of thefuel injection pulse width Tp and the injection start timing IT are sentto the fuel injection valve drive unit 35. Also, in block 364, theignition timing is determined according to the operation condition ofthe engine, and a signal of the ignition timing is sent to the ignitioncoil 34. The fuel injection start timing IT is, as shown in FIG. 10,determined during the intake stroke and the compression stroke accordingto the operation condition of the engine so as to correspond to thecombustion system of each operation condition, and the number ofinjections N_(I), is also determined (four times in FIG. 15). That is tosay, the combustion method (combination of Tp, IT, θ_(Ad), etc.) in thecombustion chamber 13 is changed in response to the operation condition.

[0081] In a low-load region A (running at a constant speed of 60 km/h,for example), a strong swirl flow is produced (the flow dividing valve23 is fully closed) in the combustion chamber 13, and also fuel isinjected at the second half stage of the compression stroke, by whichthe stratified charge lean operation with an air-fuel ratio of about 40is performed.

[0082] In a medium-load region B (running at a constant speed of 100km/h, for example, or slight acceleration from the region A), a weakswirl flow is produced (the flow dividing valve 23 is half opened) inthe combustion chamber 13, and also fuel is injected on the intakestroke, by which the stratified charge lean operation with an air-fuelratio of about 20 to 25 is performed.

[0083] In a high-load region C (running at a constant speed of over 120km/h, for example, or slow acceleration from the region A), no swirlflow is produced (the flow dividing valve 23 is fully opened) in thecombustion chamber 13, and fuel is injected on the intake stroke, bywhich the homogeneous operation with an air-fuel ratio of about 14.7 isperformed.

[0084] In a region D of further high rotation and high load (running ata constant speed of 140 km/h, for example, or quick acceleration fromthe region A), the air-fuel ratio is made lower than 14.7.

[0085] The intensity of swirl flow includes a strong swirl flow, noswirl flow, and a weak swirl flow having an intermediate intensitytherebetween.

[0086] Next, the method for lean burn operation performed in the regionsA and B will be described with reference to FIG. 5.

[0087]FIG. 5 shows a relationship between the swirl flow and theinjected fuel spray. A swirl flow 40 generated by the main intake airpassage 21, the subsidiary intake air passage 22, and the flow dividingvalve 23 forms a transverse swirl flow in the combustion chamber 13.

[0088]FIG. 6 shows the installation position of the subsidiary intakeair passage 22.

[0089]FIG. 6(a) shows a range 21 a in which the subsidiary intake airpassage 22 can be installed. To provide an intake air resistance at thetime of high load (C, D), the subsidiary intake air passage shouldpreferably be installed so as to be closer to the edge of the mainintake air passage 21. For this reason, the subsidiary intake airpassage is installed in a range on the outside of the axis of a stem 27a of the intake valve 27.

[0090]FIG. 6(b) shows an installation method in the case where the mainintake air passage 21 is divided into two portions. The subsidiaryintake air passage 22 is provided at one portion of the main intake airpassage 21, and the opening thereof is directed into the combustionchamber 13, by which a swirl flow as denoted by an arrow mark 40 isproduced.

[0091]FIG. 6(c) shows an installation method in the case where the mainintake air passage 21 is formed into one. The subsidiary intake airpassage 22 is installed so as to be close to a tangential line at theouter periphery of the combustion chamber 13, and the opening thereof isdirected along the wall surface in the combustion chamber 13, by which aswirl flow as denoted by an arrow mark 40 is produced.

[0092]FIG. 7(a) shows a relationship between the subsidiary intake airpassage 22 and the swirl flow 40 produced in the combustion chamber 13.If an angle α of the subsidiary intake air passage 22 with respect tothe horizontal plane is large, a rotation axis 40 a of the swirl flow 40is tilted, with the result that the swirl flow 40 is not a horizontalvortex, but becomes a vortex having a slantwise component. In this case,the fuel component concentrated in the center of the combustion chamberis shifted from the centerline of the combustion chamber by the tilt ofthe rotation axis of the swirl flow.

[0093]FIG. 7(b) shows a case where the tilt angle a of the subsidiaryintake air passage 22 is small. In this case, the air passing throughthe subsidiary intake air passage 22 flows into the combustion chamberat an angle close to the horizontal, so that the tilt of rotation axisof the swirl flow can be decreased. Thereby, the fuel componentconcentrated in the center of the combustion chamber can be held untilthe second half stage of the compression stroke.

[0094]FIG. 8(a) shows a relationship between a fuel spray 41 and theswirl flow 40. As an installation angle γ (angle with respect to thehorizontal plane) of the fuel injection valve 26 becomes larger, thefuel spray 41 can be held in the center of the combustion chamber moreeasily. If the fuel injection valve 26 is located at the installationposition of the ignition plug 28, the fuel spray is surely held in thecenter of the combustion chamber. When the fuel injection valve islocated under the intake valve as in this embodiment, it is thought thatthe fuel spray goes beyond the swirl flow 40 and diffuses to theperipheral portion in the combustion chamber depending on thepenetration of the spray. Therefore, a condition in which the fuel spraydoes not go beyond the swirl flow must be considered. This condition isdescribed later.

[0095]FIG. 8(b) shows a method in which the injection direction of thefuel spray is deflected to prevent the diffusion of the fuel spray tothe peripheral portion in the combustion chamber. Since a fuel spray 41a is injected so as to be tilted through an angle θ with respect to theinstallation angle γ of the fuel injection valve, the fuel spray iseasily taken into the swirl flow 41 a. If the fuel spray is usedtogether with a spray using an atomizer or a spray of short penetrationshown in FIG. 14(b), the fuel spray can surely be held in the center ofthe combustion chamber.

[0096]FIG. 9 shows another method for producing the swirl flow. The mainintake air passage 21 is divided into two passages, a main intake airpassage provided with a flow dividing valve 42 and a subsidiary intakeair passage provided with a notched valve 43, to communicate with thetwo intake valves 27. The flow dividing valve 42 and the notched valve43 are connected to each other by one shaft so that the degree ofopening of the valves can be regulated by the rotation of the shaft.When the valves are fully closed, air is introduced only through theintake air passage provided with the notched valve. Therefore, the flowvelocity is increased, so that a strong swirl flow is formed in thecombustion chamber 13. When the valves are fully opened, air isintroduced through both the passages, so that the occurrence of theswirl flow is stopped. Although the main intake air passage and thesubsidiary intake air passage are provided in FIG. 9, a constructionwithout the subsidiary intake air passage is also possible.

[0097] In both of the above-described two methods for producing theswirl flow, the air flow velocity in the vicinity of the cylinder wallsurface of the combustion chamber 13 is high, and that in the centralportion is low. If fuel is injected after the first half stroke of thecompression stroke (when the swirl flow is established), at which theswirl flow becomes strong, the fuel spray 41 injected to the portionnear the center of the combustion chamber 13 does not diffuse, andconcentrates in the swirl flow. It is important that at this time, thefuel spray 41 decelerates in the vicinity of the center of thecombustion chamber, and does not arrive at the cylinder wall on theopposite side. For such a spray, the penetration thereof shouldpreferably be 60 mm or less 3.8 msec after the fuel is injected to theatmosphere of the atmospheric pressure. Also, the spray particle size atthis time should preferably be 20 μm or smaller in terms of Zauter meanparticle size D32.

[0098] The Zauter mean particle size is defined as a particle sizecalculated from the volume and the surface area when the spray particleis assumed to be a perfect sphere. It can easily be measured by using ameasuring instrument such as a Phase Doppler Particle Analyzer (PDPA) ora Malvern particle analyzer. The numeral shown in the embodiment is theZauter mean particle size measured at a position 50 mm below the nozzletip.

[0099] To obtain such fuel spray characteristics, an atomizer as shownin FIGS. 17 to 32 should preferably be used. The use of such an atomizertends to weaken the penetrating force of spray. The atomizer itself willcollectively be described later.

[0100] The following is a description of a case where an atomizer isused.

[0101]FIG. 10 shows a control method at the time of lean burn operation.The abscissas denote the crank angle of the engine for a period from theintake stroke to the compression stroke. The ordinates denote theintensity of the swirl flow produced in the combustion chamber. Theswirl flow in the combustion chamber is affected by the degree ofopening of the intake valve during the intake stroke, and becomesstrongest in a period from the second half stage of the intake stroke tothe first half stage of the compression stroke. Thereafter, theintensity of the swirl flow decreases.

[0102] In the region A, because the stratified charge burn operation isperformed, fuel is injected as denoted by a pulse 51 when the swirl flowin the combustion chamber is established. The fuel injection amount andthe injection timing are determined so that the exhaust amount of HCdoes not increase.

[0103] In the region B, the homogeneous lean burn operation isperformed. At this time, the air-fuel ratio is 20 to 25, and fuel isinjected on the intake stroke as denoted by a pulse 52 to reduce theexhaust amount of NOx. The fuel injected during the intake stroke isagitated by the swirl flow and is diffused in the combustion chamber,thereby being mixed uniformly.

[0104]FIG. 11 shows the fuel spray characteristics for a cylinderinjection engine. The abscissas denote the average particle size ofspray, usually denoted in terms of the Zauter mean particle size D32.The ordinates denote the penetration or the spray arrival distance,denoting the spray length 3.8 ms after injection. The spraycharacteristics of an upstream swirling type injector widely used for adirect injection engine at present fall within a range 55 by changingthe fuel pressure, spray angle, and spray swirl force. With the use ofan atomizer, the spray characteristics fall within a range 56, whichmeans that the particles are made fine. However, such a spray presents aproblem in that the fuel spray is caused to flow to the intake air atthe time of full-open output, so that the mixture becomes nonuniform.

[0105]FIG. 12 shows the outline of the observation result of spraybehavior in the combustion chamber of the engine. FIG. 12(a) shows acase where the penetrating force of spray is strong, and FIG. 12(b)shows a case where the penetrating force of spray is weak. At the timeof high load, the operation of the swirl flow generating means isstopped, that is, the flow dividing valve is opened fully. Thereby, theintake air amount is increased. Vertical swirl flows 40 a and 40 b areproduced in the combustion chamber 13 by the flow passing through theupper side of the intake valve and the flow passing through the lowerside thereof. The swirl flow 40 a is an air flow having passed throughthe upper side of the intake valve, and the swirl flow 40 b is a flowhaving passed through the lower side thereof. In the case shown in FIG.12(a) where the penetrating force of spray is strong, the fuel spray isspread in the cylinder by the penetrating force of the spray itself, sothat it is diffused uniformly in the cylinder by going with the flow ofthe air flow 40 a, by which satisfactory combustion can be provided. Ifsuch satisfactory combustion can be provided, the output can be takenout with a high efficiency with respect to the supplied fuel. However,in the case shown in FIG. 12(b) where the penetrating force of spray isweak, the fuel spray is caused to flow by the flow of the air flow 40 b,so that it cannot be diffused widely in the cylinder, by which a problemis caused in that the distribution of mixture becomes nonuniform (nothomogeneous). Therefore, the injection timing is contrived as shown inFIG. 13.

[0106]FIG. 13 shows a relationship between intake air velocity andinjection pulse at the time of high load. The abscissas denote the crankangle of the engine on the intake stroke. The ordinates denote theapproximate velocity of the intake air passing through the opened areaof the intake valve. Since the opened area of the intake valve is firstsmall, the velocity is high, and thereafter decreases. At the middlestage of the intake stroke, the intake air amount increases, so that thevelocity increases again. Subsequently, the velocity decreases again,and increases before the intake valve is closed. Thereafter, the intakevalve is closed. Since the charge efficiency in natural intake is about70 to 80%, there is still a margin of intake, and the flow velocity ishigh even immediately before the intake valve is closed. In a spray withthe spray characteristics using an atomizer denoted by the region 56 inFIG. 11, the spray velocity is low (the penetrating force is weak), sothat the spray is easily caused to flow by the intake air. If the sprayvelocity is higher than the intake air velocity, the spray is preventedfrom being caused to flow by the intake air flow. The spray velocitydepends on the nozzle construction and the fuel pressure, and isindependent of the engine rotational speed. Therefore, if fuel isinjected at the above-described timing at which the intake air velocitychanges and becomes lower than the spray velocity, the influence of theintake air on the spray can be reduced. Since the intake air velocitychanges as denoted by a curve 60, the period of time when the intake airvelocity becomes lower than the spray velocity determined by the nozzleconstruction and the fuel pressure provides the injection allowablerange. By carrying out control in this manner, the injected fuel can beprevented from being deflected, so that a homogeneous mixture can beformed. When the injection allowable range is narrow and a necessaryamount of fuel cannot be injected at a time, fuel can be injectedadditionally as denoted by reference numeral 61.

[0107] The spray velocity is a velocity of fuel spray when the fuelspray is injected from the fuel injection valve into the atmosphericair. This spray velocity can be calculated by measuring the length fromthe tip end of the fuel injection valve to the tip end of the sprayevery unit time when the fuel spray is photographed by a high-speedcamera. Also, the intake air velocity is a flow velocity of intake airwhen the intake air passes through the opening of the intake valve, andis changed by the degree of opening of the valve. Therefore, in order tomeasure the intake air velocity, a steady-state air flow is supplied tothe engine head, and the degree of opening of the valve is changed, bywhich the intake air velocity is measured by using a hot wire flowvelocity meter or the like.

[0108] FIGS. 14 to 16 show the embodiment in which no atomizer is usedand an upstream swirling type injector is used. This corresponds to acase where the penetrating force of spray is strong.

[0109]FIG. 14(a) shows a state in which a spray grows when fuel isinjected by one injection using the upstream swirling type injector. Thetip end portion of a spray 41 a is subjected to air resistance, anddecelerates gradually. However, since the spray is injectedcontinuously, the spray is carried away by the subsequently injectedspray, so that the penetration becomes long. The penetration at thistime is in the range of the spray characteristics 55 shown in FIG. 11.

[0110]FIG. 14(b) shows a case where the same injection amount isinjected at four times. The first injected spray 41 a is subjected toair resistance and decelerates. The fuel is injected at multiple stages,so that the penetration becomes short because the spray 41 a is notcarried away continuously. Subsequently injected sprays 41 b, 41 c and41 d are also subjected to the same operation, so that the penetrationof the whole spray becomes shorter than the case where the fuel isinjected at a time.

[0111]FIG. 15 shows a relationship between the intensity of swirl flowin the combustion chamber and the injection pulse. In a region A wherestratified charge combustion is produced, fuel is injected when theswirl flow is established. At this time, since the penetration isshortened by the divided injection, the fuel spray is contained in theswirl flow, so that it can be prevented from diffusing. In a region Bwhere homogeneous lean operation is performed, fuel is injected beforethe swirl flow is established so that the injected fuel is mixeduniformly. At this time as well, the penetration is decreased by dividedinjection of fuel, whereby the fuel spray can be prevented from stickingto the piston and the cylinder wall.

[0112]FIG. 16 shows a relationship between intake air velocity andinjection pulse at the time of a high load (C, D). Since a strongerpenetrating force of spray provides proper mixing with air at the timeof a high load, the divided spray is stopped, and the injection timingis set as denoted by reference numeral 71 so that the intake air amountis increased most by intake air cooling, whereby the output can beincreased.

[0113] As described above, by changing the combustion method in thecombustion chamber 13 according to the operation condition, a problemcan be overcome in that fuel sticks to the piston and thereby theexhaust amount of HC is increased in the regions A and B where the leanburn operation is performed. Also, the mixture distribution in thecombustion chamber is made uniform in the regions C and D where thehomogeneous operation is performed, whereby the output can be increased.At this time, the penetration can be shortened by employing an atomizeror a divided injection. A stratum of air is formed between the shortenedpenetration and the top face of piston, thereby restraining the stickingof fuel. Also, if a stratum of air flow is positively formed on the topface of piston and on the wall surface in the combustion chamber byusing the swirl flow, the sticking of fuel can be reduced further. Byforming the stratum of air or the stratum of air flow in this manner,the adhesion of fuel to the piston can be reduced. As a result, unburnedcomponents of fuel can be reduced, and the cooling operation of pistoncan be decreased. The stratum of air flow is formed more easily when aflat piston without cavity is used than when a piston with cavity isused. Also, the fuel spray is atomized and is made liable to be affectedby the swirl flow, by which the fuel spray can be maintained in theswirl flow to provide stable and proper combustion.

[0114] When the engine control unit 36 is supplied with intake airamount Q_(a) or intake pipe pressure P and air-fuel ratio A/F inaddition to the crank angle signal and the acceleration stroke, feedbackcontrol can be carried out so that the air-fuel ratio A/F has a constantvalue (for example, 14.7) to control the engine torque so as to be thetarget torque. Also, when the control unit 36 is supplied withcombustion chamber pressure or knock sensor signal, the occurrence ofknocking is detected and can be used for the control of ignition timing.Also, if the control unit 36 is supplied with water temperature, controlfor delaying the ignition timing can be carried out to warm up theengine at an early time.

[0115] FIGS. 17 to 32 show tip end shapes of a fuel injection valveusing an atomizer comprising of a multilayer plate. The basicconfiguration comprises several thin plates with a thickness of 0.1 to0.5 mm lapped on one another, each plate being machined as shown in thefigures. A first layer of the multilayer plate has an operation suchthat fuel is spread transversely and the penetrating force of fuel isdecreased. The shapes of holes in the plates of a second and subsequentlayers serve for controlling the spray shape and for atomization. Also,one plate with a thickness of 1.0 to 1.5 mm is drilled from both sidesby laser beam machining or electrical discharge machining, by which afuel passage hole similar to the fuel passage hole extending from thetop face of the multilayer plate to the side thereof can be formed.Reference numeral 2 in the figures denotes a nozzle for the fuelinjection valve, which has a single hole 1. To the tip end thereof isattached a multilayer plate of a variety of shapes.

[0116] The material of the multilayer plate is preferably a stainlesssteel, and the several plates are preferably joined by welding. Also, asan alternative method, silicon wafers processed by etching can be joinedwith an adhesive to produce the multilayer plate.

[0117]FIG. 17 shows a four-hole diffusion type multilayer plate. Thefuel flowing out of the nozzle hole 1 spreads transversely in anintermediate chamber 5 formed in a plate 3, and ejects from ejectionholes 6 formed in a plate 4. Although the plate formed with fourejection holes is shown, two or more holes may be formed. The ejectionholes have an angle denoted by an arrow mark 7 so that fuel is ejectedto the outside. Therefore, the ejected fuels do not collide with eachother.

[0118]FIG. 18 shows a hole position shifting type multilayer plate. Thefuel flowing out of the nozzle hole 1 spreads transversely in anintermediate chamber 5 formed in a plate 3, passes through ejectionholes 6 formed in a plate 4, and ejects from ejection holes 7 formed ina plate 8. Although the plate formed with four ejection holes is shown,two or more holes may be formed. The ejection holes 6 and 7 are arrangedso as to shift from each other, and the sum of the opening area thereofis determined so as to be equal to or smaller than the cross sectionalarea of the single hole 1.

[0119]FIG. 19 shows a multi-hole type multilayer plate. The fuel flowingout of the nozzle hole 1 spreads transversely in an intermediate chamber5 formed in a plate 3, and ejects from ejection holes 6 formed in aplate 4. Although the plate formed with twelve ejection holes is shown,two or more holes may be formed. Also, although the ejection hole 6 isformed in parallel with the nozzle axis, the ejection hole may beinclined.

[0120]FIG. 20 shows a flow path change type multilayer plate. The fuelflowing out of the nozzle hole 1 spreads transversely in intermediatechambers 5 and 6 formed in plates 3 and 4, respectively, and ejects fromejection holes 7 formed in a plate 8. Although the plate formed withfour ejection holes is shown, two or more holes may be formed. Theintermediate chamber formed in the plate 4 has a shape denoted byreference numeral 6, and the intermediate chamber formed in the plate 3has a shape such that projecting portions as denoted by referencenumeral 5 are added to the shape of reference numeral 6. The ejectionholes 7 formed in the plate 8 are located at positions under theprojecting portions, so that the fuel flowing out of the nozzle hole 1does not arrive at the ejection holes 7 directly, and is ejected afterthe flow path is changed in the intermediate chambers 5 and 6. Bychanging the flow path in the intermediate chambers, turbulence energyis given to the fuel.

[0121] In FIG. 21, the fuel flowing out of the nozzle hole 1 spreadstransversely in an intermediate chamber 5 formed in a plate 3, andejects from square ejection holes 6 formed in a plate 4. In the case ofthis nozzle, the effect of fuel atomization is larger when the fuelflowing through the nozzle hole 1 is swirled.

[0122] In FIG. 22, the fuel flowing out of the nozzle hole 1 spreadstransversely in an intermediate chamber 5 formed in a plate 3, andejects from ejection holes 6 formed in a plate 4. Although the plateformed with four ejection holes is shown, two or more holes may beformed. In the case of this nozzle as well, the effect of fuelatomization is larger when the fuel flowing through the nozzle hole 1 isswirled.

[0123]FIG. 23 shows a slit type multilayer plate. The fuel flowing outof the nozzle hole 1 spreads transversely in an intermediate chamber 5formed in a plate 3, passes through a slit 6 formed in a plate 4, andejects from a slit 7 formed in a plate 8. The fuel flowing from the slit6 into the slit 7 ejects after once spreading transversely in the slit7. Therefore, the ejected fuel spray has a very thin film shape. Thecrossing angle between the slits is preferably 90 degrees.

[0124]FIG. 24 shows a four-hole slit type multilayer plate. This typewas derived based on the same concept as that of the slit type shown inFIG. 12. The fuel flowing out of the nozzle hole 1 spreads transverselyin an intermediate chamber 5 formed in a plate 3, passes through fourslits 6 formed in a plate 4, and ejects from four slits 7 formed in aplate 8. The fuel flowing from the slit 6 into the slit 7 ejects afteronce spreading transversely in the slit 7. The crossing angle betweenthe slits is preferably 90 degrees.

[0125]FIG. 25 shows a four-hole slit type multilayer plate. The fuelflowing out of the nozzle hole 1 spreads transversely in an intermediatechamber 5 formed in a plate 3, and ejects from slits 6 formed in a plate4. In case of this nozzle, the effect of fuel atomization is larger whenthe fuel flowing through the nozzle hole 1 is swirled.

[0126]FIG. 26 shows a two-hole slit type multilayer plate. This type wasderived based on the same concept as that of the slit type shown in FIG.12. The fuel flowing out of the nozzle hole 1 spreads transversely in anintermediate chamber 5 formed in a plate 3, passes through a slit 6formed in a plate 4, and ejects from slits 7 formed in a plate 8. Sincethe fuel flowing from the slit 6 into the slits 7 ejects after oncespreading transversely in the slit 7, the ejected fuel spray from oneslit has a very thin film shape. Therefore, as the whole spray, a spraywith a thickness is formed. The crossing angle between the slits ispreferably 90 degrees.

[0127]FIG. 27 shows a four-hole independent swirl type multilayer plate.The fuel flowing out of the nozzle hole 1 spreads transversely in anintermediate groove 5 formed in a plate 3, passes through ejection holes6 formed in a plate 4 and swirl groove 7 formed in a plate 8, and, afterbeing given a swirling force, ejects from ejection holes 10 formed in aplate 9. Although the plate formed with four ejection holes is shown,two or more ejection holes may be formed.

[0128]FIG. 28 shows a four-hole collision type multilayer plate. Thefuel flowing out of the nozzle hole 1 spreads transversely in anintermediate chamber 5 formed in a plate 3, and ejects from ejectionholes 6 formed in a plate 4. Although the plate formed with fourejection holes is shown, two or more ejection holes may be formed. Theejection holes have an angle denoted by an arrow mark 7 so that fuel isejected to the inside. Therefore, the ejected fuels collide with eachother in the vicinity of the tip end of nozzle.

[0129]FIG. 29 shows an eight-hole collision type multilayer plate. Thefuel flowing out of the nozzle hole 1 spreads transversely in anintermediate groove 5 formed in a plate 3, and ejects from ejectionholes 6 formed in a plate 4. Although the plate formed with eightejection holes is shown, two or more ejection holes may be formed. Theeight holes have an angle such that the ejected fuels collide with eachother at a point 7.

[0130]FIG. 30 shows a spray resonance type multilayer plate. The fuelflowing out of the nozzle hole 1 spreads transversely in an intermediatechamber 5 formed in a plate 3, and ejects from an ejection hole 6 formedin a plate 4. The fuel spreading transversely in the intermediatechamber 5 and the fuel ejecting from the ejection hole 6 resonate, andturbulence energy is given to the fuel. The resonance wavelength changesdepending on the size of the intermediate chamber.

[0131]FIG. 31 also shows a spray resonance type multilayer plate. Thefuel flowing out of the nozzle hole 1 spreads transversely in anintermediate chamber 6 formed in a plate 4, and ejects from an ejectionhole 7 formed in a plate 8. A plate 3 is formed with a single hole withthe same inside diameter as that of the nozzle hole 1 to change adistance from a valve seat of the fuel injection valve to theintermediate chamber 6. Thereby, the resonance frequency of the fuelspreading transversely and the fuel ejecting from the ejection hole 7 ischanged.

[0132]FIG. 32 shows a flow path change type multilayer plate. The fuelflowing out of the nozzle hole 1 spreads transversely in an intermediatechamber 5 formed in a plate 3, passes through a slit 6 formed in a plate4, and flows into an intermediate chamber 7 formed in a plate 8. Theintermediate chamber 7 has a shape such that projecting portions 7 areadded to the shape of the intermediate chamber 5. The fuel having passedthrough the slit 6 is divided into two flows, a flow along the outerperiphery of the intermediate chamber 7 and a flow along the projectingportion from the center. By these two flows, the fuel is swirled nearthe inlets of ejection holes 10 formed in a plate 9.

[0133] In the above-described embodiment, the thickness of the plates 3,4, 8 and 9 may be about 0.1 to 0.3 mm.

[0134] As the system for atomization, a thin film atomization system, acollision atomization system, a swirl atomization system, and anatomization system utilizing turbulence are available. In FIGS. 23 to26, the thin film atomization system is used, in FIGS. 28 and 29, thecollision atomization system is used, in FIGS. 20 to 22, 27, and 32, theswirl atomization system is used, and in FIGS. 17 to 19, 30, and 31, theatomization system utilizing turbulence is used.

[0135] Another embodiment of the present invention will be describedbelow with reference to FIG. 33 and the following drawings.

[0136]FIG. 33 is a block diagram of another embodiment. FIG. 33 is aperspective view of an engine in accordance with the embodiment. Themain components include a notched valve 43, serving as air flowgenerating means for generating air flow in a combustion chamber 13, ashaft 43 a, a partitioning plate 44, a fuel injection valve 26 forinjecting fuel into the combustion chamber 13, and a piston 12 having atop face shape such that a sufficient tumble strength can be provided.At the upper part of the combustion chamber 13, that is, on the sideopposite to the piston 12, two intake valves 27, two exhaust valves 29,an ignition plug 28, and a fuel injection valve 26 are provided. For thecombustion chamber 13 formed by these elements, the volume thereof ischanged by the reciprocating motion of the piston 12. When the piston 12lowers with the intake valves 27 being opened, air is sucked throughintake ports 21. The amount of air sucked into the combustion chamber 13is measured by an air amount sensor (not shown), and the amount of fuelinjected from the fuel injection valve 28 is determined based on themeasured value. Two intake valves 27 are provided to increase the amountof intake air. The intake ports 21 form flow paths communicating withthe two intake valves 27. The fuel injection valve 26 is installedbetween these flow paths, that is, between the two intake valves 27.Reference numeral 14 a denotes a crankshaft of an engine, which shows anexample for a four-cylinder engine. Reference numeral 14 b denotes theaxis of the crankshaft 14 a, and 14 c denotes the axis of a piston pinof the piston 12. The fuel injection valve 26 is installed so that theaxis thereof is perpendicular to the axis 14 c of the piston pin or theaxis 14 b of the crankshaft. The axis of the fuel injection valve 26 isinclined toward a lower portion of the ignition plug 28, which isinstalled at the upper part of the combustion chamber 13, so that fueleasily concentrates around the ignition plug 28. By this configuration,in injecting on the intake stroke, fuel can be distributed widely in thecombustion chamber 13, and in injecting on the second half stage of thecompression stroke, sprays can be concentrated easily in the directionof the ignition plug 28. A tumble flow concentrated in the combustionchamber turns to a stratum of air flow on the piston 12, producing anair wall. The fuel spray is conveyed in the direction of ignition plugby this air flow. Further, the fuel spray is prevented from sticking tothe piston top face because it is guided by the air wall. This system isreferred to as a tumble air guide system. The spray shape and theinjection direction of the fuel spray are set so that the fuel sprayeasily reaches the periphery of a plug gap of the ignition plug 28.

[0137] FIGS. 34 to 37 show configuration examples of tumble generatingmeans. FIG. 34 shows a configuration in which a subsidiary intake airpassage 22 is provided in the intake port 21. When the intake valves 27are opened and the piston 12 lowers, air is sucked through the intakeports 21 and the subsidiary intake air passages 22. Although not shownin the figure, by closing valves installed in the intake ports 21, theair flow through the intake ports 21 is weakened, and the air flowthrough the subsidiary intake air passages 22 is strengthened. Since theinside diameter of the subsidiary intake air passage 22 is set to besmaller than that of the intake port 21, the flow velocity of airflowing through the subsidiary intake air passage 22 is high. The mainflow of air flowing out of the subsidiary intake air passage 22, whichis as denoted by an arrow mark 40, has an influence on the ambient air40 c, generally forming a tumble flow.

[0138]FIG. 35 shows a configuration in which the subsidiary intake airpassage 22 is provided in the intake port 21, in which a case where thesubsidiary intake air passage 22 is short is shown. In this case, themain flow of air going out of the subsidiary intake air passage 22 is asdenoted by reference numeral 40, and conveys the ambient air 40 c, but aflow 40 d whose velocity is relatively low is produced undesirably. As aresult, the air flow has a poor directivity as compared with the casewhere the subsidiary intake air passage 22 is long, so that a tumbleflow necessary for the tumble air guide system is not formed.

[0139]FIG. 36 shows a configuration in which the notched valve 43 isprovided at an intermediate position of the intake port 21. The notchedvalve 43 is fixed to the shaft 43 a penetrating the intake port wall soas to be opened and closed by rotating the shaft 43 a. When the notchedvalve 43 is closed, the passage of lower half of the opening of theintake port 21 is closed. Thereby, the flow velocity of intake air isincreased. The notched valve 43 a is inevitably located at a positiondistant from the intake valve 27 because of the construction of theengine head. Therefore, although the main flow is as denoted byreference numeral 40, the flow expands immediately after passing throughthe notched valve 43, producing a flow denoted by reference numeral 40d, so that the air flow has a poor directivity.

[0140]FIG. 37 shows a configuration in which the notched valve 43 isprovided at an intermediate position of the intake port 21, and thepartitioning plate 44 is provided to prevent the diffusion of flow afterthe air flow passes through the notched valve 43. By this configuration,the air passage is formed so as to be kept smaller than the intake port21 to a position near the intake valve 27, so that the flow velocity ofair is increased. The main flow, which is as denoted by an arrow mark40, has an influence on the ambient air 40 c, generally forming a tumbleflow. The notched valve 43 is referred to as a tumble control valve.

[0141]FIG. 38 shows a comparison result for the performance of tumblegenerating means. The tumble ratio denoted on the ordinate is defined bythe number of vertical rotations of air flow during one reciprocatingmotion of piston (from the intake stroke to the compression stroke).Therefore, the larger numerical value denotes a stronger tumble airflow. In the case of the subsidiary intake air passage, the longersubsidiary intake air passage 22 provides a higher tumble ratio, and inthe case of the tumble control valve 43, the presence of thepartitioning plate 44 provides a higher tumble ratio. This is because ofa construction for preventing the diffusion of flowing-in air to aposition near the intake valve. Therefore, by the above-describedconfiguration, a tumble air flow necessary for the air guide system ofthe present invention can be generated.

[0142]FIG. 39 shows a tumble air flow generated in the combustionchamber 13 when the piston top face is flat. An object of the tumblegenerating means shown in FIGS. 34 to 37 is to generate the tumble airflow 40 having directivity in the combustion chamber 13. On the actualintake stroke, however, there exists an air flow 40 b which passesthrough the lower side of the intake valve 27 and flows into thecombustion chamber. This air flow 40 b is a flow in the directionopposite to the flow 40, that is, an inverse tumble flow, which weakensthe tumble flow necessary for the tumble air guide system of the presentinvention. It is preferable that the inverse tumble flow 40 b bereduced, or the influence thereof be lessened. Sometimes, however, it isdifficult to reduce the inverse tumble flow 40 b depending on the shapeof the intake port. If the tumble air flow 40 can be generated morestrongly, the influence of the inverse tumble flow 40 b can be lessened.

[0143]FIG. 39(a) is a schematic view showing air flows at the bottomdead center (180 deg BTDC) of the intake stroke. The air flow 40 havingdirectivity, which has passed through the tumble generating means, goesalong the cylinder wall on the exhaust side, and the direction thereofis changed by the piston top face. When the piston top face is flat, thedirection of the air flow 40 is changed through about 90 degrees,preventing smooth flow. Therefore, as shown in FIG. 39(b), at the secondhalf stage of the compression stroke (60 deg BTDC), the flows 40 and 40b cancel each other. To solve this problem, some consideration is neededto strengthen the air flow 40.

[0144]FIG. 40 shows a piston top face improved to strengthen the airflow 40. The fuel injection valve 26 and the ignition plug 28 denote thepositional relationship such that they are installed on the engine head.

[0145]FIG. 40(a) shows the piston top face which is curved to smoothenthe flow on the piston top face. A chain line 47 is parallel with thecrankshaft of the engine, and a chain line 46 is perpendicular to thechain line 47. A chain line 45 lies on the same plane as that of thechain line 46, and passes through the center of the fuel injection valve26. The top face of the piston 12 has a arcuate shape 12 a with a point48 being the center. As a result, the outer peripheral portion 12 b ofthe piston top face is as denoted by reference numeral 12 c. By thisshape, the direction of the tumble air flow 40 is changed smoothly,preventing the flow from being weakened.

[0146]FIG. 40(b) shows the piston top face which is formed with a groove12 d to prevent the tumble air flow 40 from diffusing in the directionof the chain line 47. The groove 12 d is parallel with the chain line46, and is provided so that the air flow 40 is blown up toward the fuelinjection valve 26. By providing such a shape of the piston top face,the direction of the air flow 40 is changed smoothly, preventing theflow from being weakened. As an effect of this improvement, an airstratum can be formed on the piston top face to prevent the fuel sprayfrom sticking to the piston, and the fuel spray can be conveyed towardthe ignition plug.

[0147]FIG. 41 is a schematic view showing a mixing state in thecombustion chamber 13 of an air guide type direct injection engine inaccordance with the present invention. The tumble generating meansinstalled in the intake port 21 is composed of the notched valve 43, theshaft 43 a, and the partitioning plate 44.

[0148] When the notched valve 43 is closed, most of the intake airduring the intake stroke passes through the upper side of thepartitioning plate 44, and flows into the combustion chamber. As aresult, a tumble air flow 40 is formed in the combustion chamber 13. Theair flowing into the combustion chamber on the intake stroke on whichthe intake valve 27 is open flows along the wall surface of combustionchamber on the side distant from the fuel injection valve 26, that is,on the side of the exhaust valve 29. The piston top face is formed intoan arcuate shape so that the air flow 40 flows smoothly, and is furtherformed with a groove for preventing the diffusion. By thisconfiguration, an air stratum is formed on the piston top face,preventing the fuel from sticking thereto. Further, the air flow 40blows up toward the fuel injection valve 26, and flows along the wallsurface of combustion chamber on the side on which the fuel injectionvalve 26 is installed, and the upper wall, that is, the ceiling wall ofthe combustion chamber 13, producing a swirl flow. A fuel spray 41 isconveyed toward the ignition plug by this swirl flow. As a result, thespray can reach the plug gap of the ignition plug 28 regardless of thepiston position, that is, regardless of the engine rotational speed.This relationship is determined only the distance from the fuelinjection position to the plug gap and the spray velocity. Therefore,the stratified charge operation can be performed up to a high rotationregion of 3200 rpm.

[0149] The tumble air flow 40 used in the present invention once reachesthe wall surface of combustion chamber on the side of the exhaust valvein the combustion chamber 13 after going into the combustion chamber,and then returns to the intake side along the shape of the piston topface. Therefore, the fuel spray 41 injected from the fuel injectionvalve 26 installed between the intake valves 27 reaches the ignitionplug 28 through the minimum distance while being borne by the air flow.If the fuel injection valve 26 is located on the side of the exhaustvalve 29, the fuel spray 41 flows to the side of the intake valve alongthe piston top face, and reaches the ignition plug 28. Therefore, thetime from when the fuel spray 41 is injected to when it reaches theignition plug is prolonged. Further, there is undesirably a possibilityof the fuel sticking to the piston top face.

[0150] In an experiment conducted by using an air guide type directinjection engine in accordance with the present invention, under theoperation condition of a rotational speed of 1400 rpm and an denotedmean effective pressure Pi of 320 kPa, the injection timing (FIG. 41(a))and the ignition timing (FIG. 41(b)) at which operation can be performedstably are 70 deg BTDC and 35 deg BTDC, respectively. At this time, thetime taken from injection to ignition is about 3 msec. Under theoperation condition of a rotational speed of 3200 rpm and an denotedmean effective pressure Pi of 350 kPa, they are 90 deg BTDC and 30 degBTDC, respectively. At this time, the time taken from injection toignition is about 3.12 msec. Therefore, on the air guide type directinjection engine in accordance with the present invention, the timetaken from injection to ignition is generally about 3 msec regardless ofthe engine rotational speed.

[0151] The following is a description of the fuel spray using the airguide system in accordance with the present invention.

[0152]FIG. 42 schematically shows a state of fuel spray injected fromthe fuel injection valve 26 installed in the engine. A fuel spray 41shows a spray shape when the ambient atmosphere has the atmosphericpressure, and a fuel spray 41 p shows a spray shape at a pressure of 0.6Mpa. On the intake stroke and at the first half stage of the compressionstroke, since the pressure in the combustion chamber 13 is nearly equalto the atmospheric pressure, the fuel spray is as denoted by referencenumeral 41. At the second half stage of the compression stroke, thevolume of the compression chamber 13 is decreased by the rise of thepiston 12, thereby increasing the pressure. Although the ambientpressure varies from 0.1 to 1.0 Mpa depending on the injection timing,the spray shape at a pressure of 0.6 Mpa is shown to identify the sprayshape. The spray angle of the fuel spray 41 under the atmosphericpressure is denoted by X1+X2, and the spray angle of the fuel spray 41 punder a pressurized condition is denoted by Y1+Y2.

[0153]FIG. 44 shows a method for measuring the spray angle. A triangleis formed by a nozzle tip end point A of the fuel injection valve 26 andspray contour points 25 mm down from the point A, and the vertical angleof this triangle is defined as the spray angle. In the case of the fuelspray 41, the spray angle is an angle made by connecting points B-A-E,and in the case of the fuel spray 41 p, the spray angle is an angle madeby connecting points C-A-D.

[0154] Referring to FIG. 42, the fuel injection valve 26 is installed inthe engine at an angle A with respect to the horizontal plane. The angleA is referred to as an installation angle. The upper wall of thecombustion chamber including the intake valve 27 is located at an angleB with respect to the horizontal plane, and the plug gap of the ignitionplug 28 is located at an angle C with respect to the horizontal plane.In the air guide system of the present invention, it is essential thatthe fuel spray reach a point around the plug gap of the ignition plug toperform the stratified charge operation. It is also essential that thefuel be prevented from sticking to the upper wall of the combustionchamber in order to reduce HC. Therefore, understanding can easily begained if the spray contour position on the side of the ignition plug isdenoted by an angle with respect to the plug gap. An angle defined bythe following equation using the angle C denoting the plug gap positionand an angle (X1−A) denoting the spray contour position is referred toas a top end angle J.

Top end angle J=(X 1−A)−C  (1)

[0155] Equation (1) denotes the top end angle under the atmosphericpressure, and the top end angle J′ under a pressurized condition isdefined by the following equation.

Top end angle J′=(Y 1−A)−C  (2)

[0156] The top end angle can be used generally for various types ofengines, not for a specific engine, because it is denoted by the sprayangle, the installation angle of the fuel injection valve, and the pluggap position.

[0157]FIG. 43 shows an experimental result for a relationship betweenthe top end angle and the engine performance. The abscissas denote thetop end angle J′ under a pressurized condition. The left-hand ordinatesdenote the combustion variation ratio Cpi, and the right-hand ordinatesdenote the exhaust concentration of hydrocarbon (HC). Cpi denotes avariation from a mean combustion pressure of about 100 to 1000 cycle.The smaller this value is, the better the combustion stability is. Thetop end angle of 0 degree means that the spray contour position islocated at the same position as the ignition plug gap position. When thetop end angle is smaller than this value, the spray contour positiondoes not reach the plug gap, so that the combustion variation ratio Cpiincreases. When the top end angle is −2 (deg) or larger, the Cpiallowable range is exceeded. At a top end angle of −2 (deg), the spraydoes not reach the plug gap. In the present invention, however, thespray actually reaches the plug gap because the spray is blown up towardthe plug gap by the action of tumble air flow. On the other hand, alower HC concentration is preferable. If the top end angle is large, thespray contour position undesirably reaches the upper wall of thecombustion chamber and the fuel sticks thereto, so that the exhaustconcentration of HC increases undesirably. It can be seen from FIG. 43that when the top end angle is +2 (deg) or larger, the HC concentrationincreases, so that the fuel sticks to the upper wall of the combustionchamber. Although the definition of the top end angle does not includethe angle B denoting the upper wall position of the combustion chamber,the upper limit value of the top end angle can be estimated by theexhaust behavior of HC. Therefore, in a range of top end angle from −2to +2 (deg) under a pressurized condition, both of the combustionvariation ratio Cpi and the HC exhaust concentration can be satisfied.

[0158] Next, a method for measuring a swirl/tumble air flow will beshown. The intensity of swirl/tumble air flow is defined as a swirlratio or a tumble ratio denoting the number of rotations of swirl ortumble air flow during the time when the engine rotates one turn. Theswirl ratio Sr and the tumble ratio Tr are expressed as

Sr=ωS/ωN, Tr=ωT/ωN

[0159] where, ωN is an engine angular speed, ωS is a swirl flow, and ωTis a tumble flow. For example, the swirl ratio Sr=1 means that the swirlflow rotates one turn during the time when the engine rotates one turn.

[0160]FIG. 45 shows a method for measuring the swirl air flow. Theengine head (an object to be measured which produces swirl or tumble airflow) is installed on the upstream side of an impulse swirl meter 450.Air is drawn by a blower, which is connected downstream so that the airamount corresponding to the engine rotational speed to be measured canflow. Thereby, a rotational torque of swirl or tumble air flow ismeasured by the impulse swirl meter 450. The impulse swirl meter 450contains a honeycomb core 451. Angular motion energy of the swirl ortumble air flow is applied to the honeycomb core 451 to rotate thehoneycomb core 451. The rotational torque at this time is taken out fromthe shaft 452, and is measured. From the measured value, the swirlintensity is calculated.

[0161]FIG. 46 is a perspective view showing one example of a directinjection type engine using the present invention. Also, FIG. 47 is aschematic view in which FIG. 46 is viewed from above the combustionchamber.

[0162] The groove 12 a is formed in the top face of the piston 12. Thisgroove 12 a is formed across the top face of the piston 12 from aposition distant from the fuel injection valve 26 to a position underthe fuel injection valve 26.

[0163] An inlet of air sucked into the combustion chamber 13, that is, asuction port 27 p is provided on the side close to the fuel injectionvalve 26 at the upper part of the combustion chamber 13.

[0164] The flow (denoted by a thick chain line) of air sucked into thecombustion chamber 13 through the suction port 27 p exhibits a verticalswirl flow which goes toward the side distant from the fuel injectionvalve 26, returns to a position under the fuel injection valve 26 alongthe groove 12 a formed in the top face of the piston 12, and furtherrises toward the ceiling wall of the combustion chamber 13 along thewall surface of the combustion chamber on the side on which the fuelinjection valve 26 is installed.

[0165] Also, two suction ports 27 p for sucking air are formed at theupper part of the combustion chamber 13, and the fuel injection valve 26is installed between the two suction ports 27 p.

[0166] The axis of the fuel injection valve 26 is inclined toward aposition under the ignition plug 28 installed at the upper part of thecombustion chamber.

[0167] The ignition plug 28 slightly shifts from the center of the upperpart of the combustion chamber to the side of an exhaust valve 30. Thereason for this is that a distance suitable for carrying the fuel fromthe fuel injection valve 26 to the ignition plug 28 is ensured. If theplug 28 is located at the center of the upper part of the combustionchamber depending on the type of engine, the distance becomes too short,so that the fuel may pass through the plug earlier than the normalignition timing.

[0168] Further, the axis of the fuel injection valve 26 is arranged soas to be perpendicular to the axis of a connecting pin for connectingthe connecting rod 14 to the piston 12, with the result that the groove12 a in the top face of the piston is formed at right angles withrespect to a hole 14 c for inserting the connecting pin.

[0169] This has an effect of keeping a balance of mass of the piston.Also, this has an advantage that even if the groove is formed, thetemperature distribution in the piston does not become ill-balanced somuch.

[0170] Air flows 40L and 40R entering the combustion chamber 13 throughthe two suction ports 27 p go toward the opposite wall so that both theair flows tend to go inside, and join into one flow 40 c when theycollide with the wall.

[0171] After joining, the air flow moves downward along the wall, and isguided to a position under the fuel injection valve 26 by a pair of wallsurfaces (denoted by broken lines in FIG. 47) forming the groove 12 a ofthe piston 12.

[0172] Then, the air flow collides with the wall on the side of the fuelinjection valve 26 and goes upward, and is guided by the ceiling of thecombustion chamber 13, the two intake valves 27, 27, or the two airflows 40L and 40R going into the combustion chamber through the twosuction ports 27 p, 27 p. Thereupon, the air flow passes between the twoair flows 40L and 40R, going from the fuel injection valve 26 to theignition plug, and is then absorbed by the air flow 40 c.

[0173] The fuel injection valve 26 injects fuel into the flow from thefuel injection valve 26 to the ignition plug 28 in such a tumble airflow 40, and the fuel is carried from the fuel injection valve 26 to theignition plug 28 by the air flow.

[0174] With this method, the distance through which fuel is carried isshort, so that there is less possibility for the fuel to stick to thewall surface of combustion chamber and the like.

[0175] In particular, the piston is isolated by two air strata, astratum of air flowing to the side of the fuel injection valve 26 bybeing guided by the groove 12 a and a stratum of air flowing from thefuel injection valve 26 to the plug 28. Therefore, the fuel scarcelyreaches the piston 12.

[0176] In the embodiment with the above-described configuration, anexperiment has revealed that the stratified charge operation by thetumble guide can be performed not only in the region of high load andhigh rotational speed as described above but also under a severecondition such as the cranking time or the cold start time.

[0177] Since the stratified charge operation can be performed at thecranking time or the cold start time, ignition can be accomplishedsurely from the first detonation, and the first misfire at the starttime does not occur at all. As a result, the harmful components ofexhaust gas can be reduced.

Industrial Applicability

[0178] The control method for an internal combustion engine inaccordance with the present invention has an excellent effect such thatfuel does not stick to the piston at the time of stratified chargecombustion, so that exhaust gas can be purified, and also a mixture canbe mixed uniformly at the time of homogeneous operation, so that theoutput can be increased. Therefore, the method is useful for theinternal combustion engine, injection valve, and other similar devices,and also is suitable for the stratified charge lean operation at thetime of high rotational speed of 120 km/h or 3200 rpm and the increasein fuel efficiency.

1. A cylinder injection type internal combustion engine comprising: acombustion chamber into which air is sucked; a fuel injection valve forinjecting fuel directly into said combustion chamber; and a piston forchanging the volume of said combustion chamber, characterized in thatsaid piston has a face allowing the flow of air to go from the side ofthe wall surface in said combustion chamber opposite to said fuelinjection valve to just under said fuel injection valve, and a stratumof the sucked air or a stratum of air flow is interposed between a fuelspray injected from said fuel injection valve and the wall surface insaid combustion chamber on the installation side of said fuel injectionvalve and between said fuel spray and the top face of said piston.
 2. Acylinder injection type internal combustion engine comprising a fuelinjection valve for injecting fuel directly into a combustion chamber ofsaid internal combustion engine, characterized in that penetration of afuel spray injected from said fuel injection valve into said combustionchamber is set to be shorter than a distance between the top face of apiston reciprocating in said combustion chamber and a fuel dischargeport of said fuel injection valve during a period of time from the startof injection to the completion of injection of fuel.
 3. A cylinderinjection type internal combustion engine comprising a fuel injectionvalve for injecting fuel directly into a combustion chamber of saidinternal combustion engine, characterized in that said fuel injectionvalve is formed so that the penetration of a fuel spray 3.8 msec afterthe injection of fuel to the atmosphere of the atmospheric pressure is60 mm or shorter.
 4. A cylinder injection type internal combustionengine comprising a fuel injection valve for injecting fuel directlyinto a combustion chamber of said internal combustion engine,characterized in that said fuel injection valve is formed so that a fuelspray with a Zauter mean particle size of 20 μm or smaller is injected.5. The cylinder injection type internal combustion engine according toclaim 3 or 4, characterized in that said fuel injection valve has anatomizer formed by lapping a plurality of plates having a circular orpolygonal hole.
 6. A cylinder injection type internal combustion engine,comprising: a combustion chamber for said internal combustion engineinto which air is sucked through an intake valve; a fuel injection valvefor injecting fuel directly into said combustion chamber; swirl flowgenerating means for generating a swirl air flow in said combustionchamber; and operation condition detecting means for detecting theoperation condition of said internal combustion engine, characterized inthat said internal combustion engine has a control unit for supplying afuel injection valve driving signal to said fuel injection valve so thatfuel is injected at the second half stage of the compression stroke whenthe detected operation condition is at a low load.
 7. A cylinderinjection type internal combustion engine comprising: a combustionchamber of said internal combustion engine, into which air is suckedthrough an intake valve; a fuel injection valve for injecting fueldirectly into said combustion chamber; swirl flow generating means forgenerating a swirl air flow in said combustion chamber; and operationcondition detecting means for detecting the operation condition of saidinternal combustion engine, characterized in that said internalcombustion engine has a control unit for supplying a fuel injectionvalve driving signal to said fuel injection valve so that fuel isinjected on the intake stroke when the detected operation state is at amedium load.
 8. A cylinder injection type internal combustion enginecomprising: a combustion chamber of said internal combustion engine,into which air is sucked through an intake valve; a fuel injection valvefor injecting fuel directly into said combustion chamber; and operationcondition detecting means for detecting the operation condition of saidinternal combustion engine, characterized in that said internalcombustion engine has a control unit for supplying a fuel injectionvalve driving signal to said fuel injection valve so that fuel isinjected for a period of time when the intake air velocity is lower thanthe spray velocity on the intake stroke when the detected operationcondition is at a high load.
 9. The cylinder injection type internalcombustion engine according to claim 8, characterized in that said fuelinjection valve has an atomizer formed by lapping a plurality of plateshaving a circular or polygonal hole, and said control unit supplies afuel injection valve driving signal to said fuel injection valve so thatfuel is injected a plurality of times before and after the timing atwhich said intake valve is fully opened.
 10. A cylinder injection typeinternal combustion engine comprising: an upstream swirl type fuelinjection valve for injecting fuel directly into a combustion chamber ofsaid internal combustion engine; and operation condition detecting meansfor detecting the operation condition of said internal combustionengine, characterized in that said internal combustion engine has acontrol unit for supplying a fuel injection valve driving signal to saidfuel injection valve so that fuel is injected at a time for a period oftime when the intake air velocity is higher than the spray velocity onthe intake stroke when the detected operation condition is at a highload.
 11. A control method for a cylinder injection type internalcombustion engine, characterized in that when the operation condition ofsaid internal combustion engine is at a low load, a swirl air flow isgenerated in a combustion chamber, fuel is injected at the first halfstage of the compression stroke, and a rich mixture stratum is formedinside said swirl air flow, whereby stratified charge lean operation isperformed.
 12. A control method for a cylinder injection type internalcombustion engine, characterized in that when the operation condition ofsaid internal combustion engine is at a medium load, a swirl air flow isgenerated in a combustion chamber, fuel is injected on the intakestroke, and a mixture with a homogeneous concentration is generated insaid combustion chamber by said swirl air flow, whereby homogeneous leanoperation is performed.
 13. A control method for a cylinder injectiontype internal combustion engine, characterized in that when theoperation condition of said internal combustion engine is at a highload, fuel having an amount capable of achieving a stoichiometricair-fuel ratio is injected for a period of time when the intake airvelocity is lower than the spray velocity on the intake stroke, and amixture with a homogeneous concentration is generated in the combustionchamber by intake air, whereby homogeneous stoichiometric operation isperformed.
 14. A fuel injection valve for injecting fuel directly into acombustion chamber of an internal combustion engine, characterized inthat a fuel spray injected from said fuel injection valve has apenetration of 60 mm or shorter 3.8 msec after the time when fuel isinjected to the atmosphere of the atmospheric pressure.
 15. A fuelinjection valve for injecting fuel directly into a combustion chamber ofan internal combustion engine, characterized in that the spray particlesize of fuel injected from said fuel injection valve is 20 μm or smallerin terms of Zauter mean particle size.
 16. The fuel injection valveaccording to claim 14 or 15, characterized in that said fuel injectionvalve has an atomizer formed by lapping a plurality of plates having acircular or polygonal hole through which fuel goes to a fuel ejectionportion of said fuel injection valve.
 17. A cylinder injection typeinternal combustion engine comprising: a combustion chamber into whichair is sucked; a fuel injection valve for injecting fuel directly intosaid combustion chamber; and a piston for changing the volume of saidcombustion chamber, characterized in that a groove is formed in the topface of said piston, said groove being formed across the top face ofsaid piston from a position distant from said fuel injection valve to aposition under said fuel injection valve, an inlet of air sucked intosaid combustion chamber is provided on the side close to said fuelinjection valve at the upper part of said combustion chamber, and theflow of air sucked into said combustion chamber through said inletexhibits a swirl flow which goes toward the side distant from said fuelinjection valve, returns to a position under said fuel injection valvealong said groove formed in the top face of said piston, and furtherrises toward the ceiling wall of said combustion chamber along the wallsurface of said combustion chamber on the side on which said fuelinjection valve is installed.
 18. The cylinder injection type internalcombustion engine according to claim 17, characterized in that valvemeans which forms a throttle for increasing the flow velocity of intakeair is provided on the upstream side of said air inlet provided at theupper part of said combustion chamber.
 19. A cylinder injection typeinternal combustion engine comprising: a combustion chamber into whichair is sucked; a fuel injection valve for injecting fuel directly intosaid combustion chamber; and a piston for changing the volume of saidcombustion chamber, characterized in that a cavity is formed in the topface of said piston, said cavity has convex portions on the side distantfrom said fuel injection valve and on the side close to said fuelinjection valve, and has a deep concave portion at an intermediateportion between said two convex portions, an inlet of air sucked intosaid combustion chamber is provided on the side close to said fuelinjection valve at the upper part of said combustion chamber, and theflow of air sucked into said combustion chamber through said inletexhibits a swirl flow which goes toward the side distant from said fuelinjection valve, returns to a position under said fuel injection valvealong said cavity formed in the top face of said piston, and furtherrises toward the ceiling wall of said combustion chamber along the wallsurface of said combustion chamber on the side on which said fuelinjection valve is installed.
 20. A cylinder injection type internalcombustion engine comprising: a combustion chamber into which air issucked; a fuel injection valve for injecting fuel directly into saidcombustion chamber; and a piston for changing the volume of saidcombustion chamber, characterized in that an inlet of air sucked intosaid combustion chamber is provided on each side of said fuel injectionvalve installed at the upper part of said combustion chamber, and theflow of air sucked into said combustion chamber through said two inletsexhibits a swirl flow which goes toward the side distant from said fuelinjection valve, returns to a position under said fuel injection valvealong the top face of said piston, and further rises toward the ceilingwall of said combustion chamber along the wall surface of saidcombustion chamber on the side on which said fuel injection valve isinstalled.
 21. A cylinder injection type internal combustion enginecomprising: a combustion chamber into which air is sucked; a fuelinjection valve for injecting fuel directly into said combustionchamber; and a piston for changing the volume of said combustionchamber, characterized in that two suction ports for sucking air areformed at the upper part of said combustion chamber, and said fuelinjection valve is installed between said two suction ports, the axis ofsaid fuel injection valve is inclined toward a position under anignition plug installed at the upper part of said combustion chamber,and the flow of air sucked into said combustion chamber through saidsuction ports exhibits a swirl flow which goes toward the side distantfrom said fuel injection valve, returns to a position under said fuelinjection valve along the top face of said piston, and further risestoward the ceiling wall of said combustion chamber along the wallsurface of said combustion chamber on the side on which said fuelinjection valve is installed.
 22. A cylinder injection type internalcombustion engine comprising: a combustion chamber into which air issucked; a fuel injection valve for injecting fuel directly into saidcombustion chamber; and a piston for changing the volume of saidcombustion chamber, characterized in that two suction ports for suckingair are formed at the upper part of said combustion chamber, and saidfuel injection valve is installed between said two suction ports, theaxis of said fuel injection valve is arranged so as to be perpendicularto the axis of a connecting rod or a piston pin of said engine, and theflow of air sucked into said combustion chamber through said suctionports exhibits a swirl flow which goes toward the side distant from saidfuel injection valve, returns to a position under said fuel injectionvalve along the top face of said piston, and further rises toward theceiling wall of said combustion chamber along the wall surface of saidcombustion chamber on the side on which said fuel injection valve isinstalled.
 23. The cylinder injection type internal combustion engineaccording to any one of claims 17 to 22, characterized in that the fuelinjection timing is set at 3.0 msec±0.5 msec before the ignition timing.